This invention relates generally to golf balls, and more specifically, to a golf ball having a cover comprising three or more layers.
The majority of golf balls commercially available today can be grouped into two general classes: solid and wound. Solid golf balls include one-piece, two-piece, and multi-layer golf balls. One-piece golf balls are inexpensive and easy to construct, but have limited playing characteristics and their use is usually confined to the driving range. Two-piece balls are generally constructed with a polybutadiene solid core and a cover and are typically the most popular with recreational golfers because they are very durable and provide good distance. These balls are also relatively inexpensive and easy to manufacture, but are regarded by top players as having limited playing characteristics. Multi-layer golf balls are comprised of a solid core and a cover, either of which may be formed of one or more layers. These balls are regarded as having an extended range of playing characteristics, but are more expensive and difficult to manufacture than are one- and two-piece golf balls.
Wound golf balls, which typically include a fluid-filled center surrounded by tensioned elastomeric material and a cover, are preferred by many players due to their spin and xe2x80x9cfeelxe2x80x9d characteristics but are more difficult and expensive to manufacture than are most solid golf balls. Manufacturers are constantly striving, therefore, to produce a solid ball that retains the beneficial characteristics of a solid ball while concurrently exhibiting the beneficial characteristics of a wound ball.
Golf ball playing characteristics, such as compression, velocity, xe2x80x9cfeel,xe2x80x9d and, therefore, spin, can be adjusted and optimized by manufacturers to suit players having a wide variety of playing abilities. For example, manufacturers can alter any or all of these properties by changing the materials (i.e., polymer compositions) and/or the physical construction of each or all of the various golf ball components (i.e., centers, cores, intermediate layers, and covers). Finding the right combination of core and layer materials and the ideal ball construction to produce a golf ball suited for a predetermined set of performance criteria is a challenging task.
Efforts to construct a multi-layer golf ball that has the benefits of both solid and wound balls have been numerous but manufacturers have generally focused on the use of cover layers formed of ionomeric compositions. It has been determined, however, that it is difficult to provide good xe2x80x9cfeelxe2x80x9d characteristics in a golf ball with the use of non-polyurethane materials, such as ionomers, which tend to provide a xe2x80x9cplastic feel.xe2x80x9d
It is desirable, therefore, to construct a golf ball formed of a thin urethane outer cover layer, at least two inner cover layers, and at least one core layer, according to the present invention. In particular, it is desired that this construction produce a multi-layer golf ball having variable spin rates, based on predetermined ball construction, while providing the golfer with good xe2x80x9cfeelxe2x80x9d characteristics generally associated with other conventional ball constructions.
A golf ball comprising a core and a cover disposed adjacent the core, wherein the cover comprises an inner cover layer having a first thickness and being disposed directly about the core; an outer cover layer having a second thickness no greater than about 0.050 inches; and an intermediate cover layer having a third thickness and being disposed between and adjacent to the inner and outer cover layers; and wherein the outer cover layer comprises a composition formed from a reactive liquid material; and the combination of the first, second, and third thickness is no greater than about 0.125 inches. Preferably, the outer cover layer has a thickness no greater than about 0.035 inches and, more preferably, no greater than about 0.025 inches.
The combination of the inner, intermediate, and outer cover layers should have a thickness of no greater than about 0.105 inches and, more preferably, no greater than about 0.090 inches. The outer cover layer, when formed, can be a castable liquid reactive thermoset material or a reaction injection molding material. If the outer cover layer is formed with a castable liquid reactive thermoset material, it preferably comprises polyurethane, polyurea, polyurethane ionomer, epoxy, or a mixture thereof. In another alternative construction, the intermediate or inner cover layers includes a reaction injection molded material.
The golf ball of the present invention can have a dual core comprising a center and at least one outer core layer or it can be a single solid center. The outer core layer, if present, may include a tensioned elastomeric material or preferably, is solid. In another embodiment, the center is liquid-filled, hollow, foam, gel-filled, or gas-filled.
The outer cover layer should have a hardness of no less than about 55 Shore D or, in an alternative construction, the outer cover layer has a hardness of no greater than about 55 Shore D. The outer cover layer may also include a thermoplastic polyurethane and the inner cover layer and intermediate cover layer may both include a thermoplastic material. If the inner or intermediate layers include a thermoplastic material, it preferably includes ionomers, polyolefins, metallocenes, polyesters, polyamides, thermoplastic elastomers, copolyether-amides, copolyether-esters, and mixtures thereof. The outer cover layer is preferably formed with a specific gravity of between about 0.8 g/cc to about 1.4 g/cc.
The golf ball of the present invention ideally has an inner cover layer having a first hardness of at least about 60 Shore D. Further, the intermediate cover layer has a second hardness and the outer cover layer has a third hardness softer than the hardness of the inner cover layer.
The inner cover layer has a first hardness, the intermediate cover layer has a second hardness, and the outer cover layer has a third hardness. In a first embodiment, the second hardness is less than about 55 Shore D and the third hardness is greater than about 55 Shore D; in a second embodiment, the second hardness is less than about 55 Shore D and the third hardness is less than about 55 Shore D; in a third embodiment, the intermediate layer has a hardness of greater than 55 Shore D and the outer cover layer has a hardness of greater than 55 Shore D; in a fourth embodiment, the intermediate layer has a hardness of greater than 55 Shore D and the outer cover layer has a hardness of less than 55 Shore D; in a fifth embodiment, the intermediate cover layer has a hardness less about 55 Shore D and the inner or outer cover layers; in a sixth embodiment, the first hardness is less than the second or third hardness; in a seventh embodiment, first hardness is less than about 60 Shore D and less than the second hardness; in an eighth embodiment, the second hardness is less than the third hardness; in a ninth embodiment, the second hardness is greater than the third hardness; in a tenth embodiment, the first hardness is less than about 45 Shore D; in an eleventh embodiment, the first hardness is greater than about 70 Shore D; and in a twelfth embodiment, the third hardness is less than about 45 Shore D, the second hardness is less than the first hardness and greater than the third hardness.
The core of the present ball has an outer diameter of about 1.40 inches to about 1.60 inches. Preferably, the core comprises an inner core layer and an outer core layer, wherein the inner core layer has a specific gravity lower than the specific gravity of the outer core layer. Alternatively, the inner core layer has a specific gravity higher than the specific gravity of the outer core layer. The core can include polybutadiene rubber, high-Mooney viscosity polybutadiene rubber, polybutadiene rubber having a trans-isomer content of greater than about 30%, and mixtures thereof.